Open hearth-room-heating devices working on closed circuit

ABSTRACT

The present invention relates to room-heating devices of the live-combustion type comprising a hearth open to the atmosphere in which the combustion is effected, and working on a closed circuit without any evacuation chimney, said device comprising in combination: suction means for creating an upward flow of the gaseous mixture formed by the primary air necessary for the combustion and the gases generated by said combustion, and solid particles or smoke also generated by said combustion and conveyed by said gaseous mixture; said gaseous mixture and said solid particles being passed through purifying means comprising devices for separating said combustion gases from said solid particles and for holding back said particles so as to deliver a purified gaseous fluid, a re-cycling circuit being coupled to the outlet of said purifying means for re-cycling the purified fluid to the hearth of said device. The invention is especially applicable to installations for apartment fireplaces.

United States Patent [191 Richard [451 Oct. 7, 1975 OPEN HEARTH-ROOM-HEATING DEVICES WORKING ON CLOSED CIRCUIT Gilbert Gerard Richard, Yerres, France [73] Assignee: Cheminees Richard le Droff S.A., Yerres, France [22] Filed: Feb. 5, 1974 [21] Appl. No.: 439,710

[75] Inventor:

[30] Foreign Application Priority Data Primary Examiner-William F. ODea Assistant Examiner-Peter D. Ferguson Attorney, Agent, or Firm-Brisebois & Kruger [57] ABSTRACT The present invention relates to room-heating devices of the live-combustion type comprising a hearth open to the atmosphere in which the combustion is effected, and working on a closed circuit without any evacuation chimney, said device comprising in combination: suction means for creating an upward flow of the gaseous mixture formed by the primary air necessary for the combustion and the gases generated by said combustion, and solid particles or smoke also generated by said combustion and conveyed by said gaseous mixture; said gaseous mixture and said solid particles being passed through purifying means comprising devices for separating said combustion gases from said solid particles and for holding back said particles so as to deliver a purified gaseous fluid, a recycling circuit being coupled to the outlet of said purifying means for re-cycling the purified fluid to the hearth of said device.

The invention is especially applicable to installations for apartment fireplaces.

23 Claims, No Drawings US. Patent Oct. 7,1975 Sheet 1 of9 3,910,252

U.S. Patent 0a. 7,1975 Sheet 2 of9 3,910,252

US. Patent 00. 7,1975 Sheet 3 of9 3,910,252

FIG-5 US. Patent Oct. 7,1975 Sheet40f9 3,910,252

US. Patent Oct. 7,1975 Sheet 5 of9 3,910,252

U.S. Patent Oct. 7,1975 Sheet 6 of9 3,910,252

US. Patent Oct. 7,1975 Sheet 7 of 9 3,910,252

US. Patent Oct. 7,1975 Sheet 9 of9 3,910,252

OPEN HEARTH-ROOM HEATING DEVICES WORKING ON CLOSED CIRCUIT The present invention relates essentially to a livecombustion heating device for a dwelling house, in particular an apartment fireplace, comprising a hearth open to the atmosphere in which the combustion is effected.

At the present time there exists a very considerable demand for apartment fireplaces which are most frequently intended for' burning wood, these fireplaces being appreciated both by reason of their decorative effect and of the note of rusticity which they introduce into modern life. Up to the present time however, the installation of an apartment fireplace presumed the existence or the creation of an evacuation conduit for the amoke, discharging into free air. Now, numerous living premises of modern construction, apartments or individual houses, are not provided with such conduits and this, up to the present time, has rendered the installation of fireplaces very difficult, if not impossible.

Furthermore, the evacuation conduits which are provided in many rooms of older construction were most frequently built on a purely empirical basis so that it frequently happens that their operation is defective. In consequence of insufficient natural draught, the gases generated by combustion, of which certain, such as carbon monoxide, are furthermore toxic, and also the smoke carried by thesegases, cannot normally be evacuated to the exterior of the room, so that a downdraught is produced from the chimney, thus dangerously polluting the atmosphere of the room in which it is installed.

The present invention has for its object to avoid these drawbacks and proposes a heating device of the type referred to above, which is especially characterized in that it comprises, in combination, suction means provided in order to create above the hearth an upward flow of the gaseous mixture constituted by the primary air necessary for combustion and the gases generated by that combustion, together with solid particles or smoke, also produced by this combustion and conveyed by the said gaseous mixture, purifying means into which pass the gaseous mixture and the solid particles which it conveys, the said purifying means being provided in order to separate and retain the said gases produced by the combustion together with the said solid particles, and to deliver at their outlet a purified gaseous fluid, and a circuit for recycling the said purified fluid, coupled to the outlet of the purifying means.

The device according to the invention creates an artificial draught, so that its operation is not in any way dependent on the good properties or even on the existence of a conduit opening into the atmosphere, which conduit is a necessity for chimneys working by natural draught.

The elimination from the gaseous mixture drawn in by the suction means of the gases produced by the combustion, that is to say of toxic or at least unhealthy gases, together with the solid particles, that is to say smoke carried by this gaseous mixture, makes it possible to obtain a purified gaseous fluid charged with heat, which can be sent back to the hearth, thereby improving the combustion and possibly permitting the reburning of the carbon monoxide which may subsist in the said fluid.

The device according to the invention is characterized by the fact that the suction means referred to comprise a static nozzle having a pressure-reducing effect, coupled to a source of fluid under pressure, for example a compressor.

A discharge nozzle of this kind is a device which is extremely simple to construct, and is thus economic and with reliable and silent operation. The regulation of its output, that is to say the regulation of the chimney draught is effected by acting on the flow-rate and the pressure of the source of compressed fluid, which permits great flexibility of operation.

The device according to the invention is also characterized by the fact that the purifying means abovementioned comprise a first and a second filtering device respectively arranged on the upstream and downstream sides of the above suction means, and coupled to these latter in a removable manner.

These first and second filtering means, the functions of which are complementary, may thus readily be replaced when the substances, devices, etc., which they comprise and which are necessary for the purification effect, are exhausted or have reached saturation.

The first filtration device preferably comprises in succession in the direction of flow of the gaseous mixture, means for retention of the solid particles, means for adsorbing gases such as H S Nl-l etc., means for fixing water vapour, porous means forming a molecular sieve for the retention of the gaseous molecules of predetermined size, and catalytic means for the conversion of the carbon monoxide to carbon dioxide.

The second filtration device referred to above comprises means for retaining the carbon dioxide by reaction of this latter with an alkaline solution with a view to the formation of a carbonate insoluble in water.

The device according to the invention effects not only the elimination of smoke and the bad-smelling or toxic combustion gases, but also the elimination of the CO by reason of the re-cycling employed, since the gaseous fluid would not be brought back to the hearth without being purified from C0 The device according to another form of embodiment of the invention, is characterized by the fact that the suction means referred to further comprise a second static nozzle placed on the downstream side of the first nozzle and constituted by a member in the form of a spherical cap arranged coaxially with the said tubular element, with its convex portion turned towards this latter so as to form a deflecting surface for the gases coming in larninary flow from the first nozzle, and cause a turbulent flow of the said gases at the outlet of the second nozzle.

This second nozzle, by causing a turbulent flow and in consequence a stirring effect on the gases, makes it possible to obtain an intimate contact of these gases with the materials of the purifying devices which are located at the outlet of the said second nozzle and especially facilitate the elimination of the carbon dioxide gas (C0 The device according to the invention has other characteristic features and numerous other advantages, which will become apparent from the subsequent description concerning a certain number of forms of application, described by way of examples and without any limitative nature, reference being made to the accompanying drawings, in which:

FIG. 1 is a diagrammatic view in cross-section of an apartment fireplace according to a first form of embodiment of the invention, provided with suction means and purification means for the combustion gases;

FIG. 2 is a diagrammatic viewin exploded perspective of the said suction means together with the filtering devices which form the said purification means;

FIG. 3 shows diagrammatically a first alternative form of construction of the filtering device for the elimination of CO FIG. 4 shows diagrammatically a second alternative form of construction of the said filtering device;

FIG. 5 shows diagrammatically a third form of embodiment of the said filtering device;

FIG. 6 shows diagrammatically a fourth alternative form of construction of the said filtering device;

FIG. 7 shows diagrammatically a fifth alternative form of construction of the said filtering device;

FIG. 8 shows diagrammatically and in cross-section a fireplace according to the invention, provided with a heat-exchanger;

FIG. 9 shows diagrammatically in cross-section an apartment fireplace in accordance with a second form of embodiment of the invention.

Referring to FIG. 1, it is seen that the apartment fireplace according to a first form of embodiment of the invention and indicated generally by the reference 1, comprises essentially a hearth 2in which the combustion is effected and a metallic casing 3 or the like, made for example of sheet steel plates arranged above the hearth 2. This casing 3 is provided at its lower portion and on its front face with an opening 4 communicating with the open atmosphere, and the casing is closed at its upper portion by a wall 5 which is preferably removable.

A conduit or duct 6 provided in the interior of the casing 3 at the rear portion of this latter, directly connects the upper part of the said casing to the hearth 2, this conduit serving for the re-cycling of gases, as will be explained later. The conduit 6 is provided at its lower portion with an orifice 7 for the admission of fresh air, communicating with the exterior, and this orifice may be closed by an oscillating shutter 7a.

Inside the casing 3 and therefore above the hearth 2 is housed an element 9 of generally cylindrical form, which comprises on the one hand suction means, indicated generally at 10, the function of which is to create an upward flow of the gaseous mixture formed by the primary air admitted through the opening 4 and the gases produced by combustion, this gaseous mixture conveying solid particles or smoke, also produced by combustion, and on the other hand purifying means placed on each side of the said suction means and indicated generally by 20 and 30 respectively, these purifying means having the function of separating and retaining the said combustion gases and also the said solid particles or smoke, so as to deliver purified air. A wall 8 closes at its lower portion the space formed between the said cylindrical element 9 and the casing 3.

The arrows F of FIG. 1 and the following figures indicate the travel of the gaseous flux circulating in the various parts of the device.

The suction means 10 referred to above comprise essentially a casing 11 of circular section, preferably of sheet steel, in the interior of which is mounted a static pressure-reducing nozzle 12 constituted by a tubular element of generally cylindrical shape, arranged coaxially with the casing 11. This tubular element 12 is provided with an internal constriction 12a into which discharges a conduit 13 supplied with compressed air from a compressor 14, arranged at the upper portion of the casing 3. The compressed air which comes into the constriction 12a is expanded at very high speed, thus creating upstream of the nozzle 12 a high depression resulting in a suction from the bottom upwards of the primary air admitted throughthe orifice 4, and of the gases produced by the combustion. Two deflectors 15 and 16 in the shape of truncated cones, are placed inside the casing 11, concentrically with this latter, repsectively on the upstream and on the downstream sides of the nozzle 12, these deflectors having the function of creating a concentric reduction of the rising flow of gas. The casing 1 1 may be permanently fixed to the casing 3 by lugs 11a.

The suction means 10 further comprise a second static nozzle 17 placed in series with the nozzle 12 and downstream of this latter. This second nozzle 17 has the form of a spherical cap arranged coaxially with the nozzle 12 and with its convex portion turned towards this latter. The nozzle 17 is supported in an adjustable manner by the deflector 16, by means of a threaded end 17a intended to be screwed on a support 16a threaded internally of the deflector 16, as shown in FIG. 2. By screwing the end member 17a more or less on its threaded support 16a, the useful passage space for the flow of gas between the deflector l6 and the nozzle 17 can be varied at will. The nozzle 17 further comprises an evacuation conduit 17b, the function of which will be explained later.

The purifying means 20 which are located upstream of the said suction means 10 and constitute the first filtering device, comprise essentially a casing 21 of circular section and provided so as to fit on the casing 11, to which it can be fixed in a removable manner by means of a retention system of any kind, for example with studs or springs, permitting easy placing in position and removal. The casing 21 is divided into superimposed stages by grids or the like such as 22, serving to support various filtering or adsorbent substances.

This first filtration element 20, known as the solid filtration element, comprises essentially, from the bottom upwards, that is to say in the direction of the flow of the rising fluid:

- a mattress 23 of wires of steel, silica or alumina, the purpose of which is to retain the solid particles, soot, smoke, etc., in suspension in the gaseous mixture;

a layer of active carbon 24, preferably in granular form, having the function of fixing the smell and certain harmful components of the gaseous mixture by adsorbing gases such as H 5;

a layer of silica gel 25 or of dehydrated substances with a micro-porous structure, which retains the water vapour in the gaseous mixture;

- a layer of porous material 26 having pores of predetermined dimensions: this material, known under the Registered Trade-Mark SILIPORITE, forms a molecular sieve absorbing certain gaseous molecules of pre-determined size, such as for example the molecules of gas produced by the combustion of plastic materials which may have been burned in the hearth 2, or alternatively compounds such as ammonia, acetylene, ethylene, etc.,

a layer of metallic oxides 27, such as for example manganese dioxide, copper oxide, cobalt oxide and silver oxide, these oxides being preferably arranged in superimposed beds which have the function of causing oxidation of the carbon monoxide and its conversion to carbon dioxide, and to polymerize certain organic compounds.

It is known that the period of service of the metallic oxides is essentially a function of the humidity. The fact of placing the layers of oxides 27 at the upper part of the filter, especially above the silica gel, enables them to be effectively protected against humidity and in consequence prolongs their service life.

This first filtration device constitutes essentially a solid filter which is the first to receive the gases to be purified and which is intended to be replaced, after a certain period of service, by a new filtration device identical but provided with new or regenerated sub stances.

The purifying means 30 which are located downstream of the suction means and constitute the second filtration device, essentially comprise a casing 31 of circular section intended to be fitted on the casing 11. This casing 31, like the casing 21, may be fixed to the casing 11 by virtue of retention means with studs or springs, permitting easy placing in position and removal.

This second filtering device 30, known as the liquid filtration element, comprises essentially an annular filter 32 constituted by a porous material such as blotting paper arranged in superimposed bands folded in a herringbone pattern. This filter has its lower portion immersed in an alkaline solution 33, for example a solution of soda or potash which fills the bottom of the filtration element 30, that is to say the annular portion between the casing 31 and the frusto-conical deflector 16. A conduit 34 enables the filtration device 30 to be supplied with alkaline solution from a tank (not shown) while an overflow orifice 35 ensures a constant level of the said alkaline solution.

The filtering device 30 is provided at its upper portion with a mattress 36 of stainless steel wires or alternatively of silica or alumina wires, which has the function of retaining the small drops in suspension of the alkaline solution vapour, by condensing them. The liquid droplets thus formed return to the bottom of the filtration device 30, either directly or through the nozzle 17 and its evacuation conduit 17b.

The filter 32 is inpregnated over the whole of its height by upward capillary action of the alkaline solution in which its lower portion is immersed.

The carbon dioxide contained in the mixture which passes through the herringboned annular filter 32 thus impregnated with alkaline solution forms, by reaction with this solution, an insoluble carbonate which is precipitated, the carbonate thus formed being deposited on the herringbones over the whole height of the filter. By virtue of this method of mounting, the filtration device 30, like the filtration device 20, can be easily replaced when the herringbones are completely blocked up by the deposit of carbonate.

The operation of the device described above is as follows: when the fire is lighted in the hearth 2, the compressor 14 is started-up and this brings the nozzle 12 into operation and starts the suction of the primary air necessary for combustion of the gases produced by the combustion and of the solid particles (smoke, suit) also produced by this combustion. The upward flow thus created passes successively through the mattress 23 which retains the solid particles in suspension, the layer 24 of activated carbon which fixes the bad smelling gases such as H- S and certain harmful gases, the layer 25 of silica gel or the like which retains the moisture, the molecular sieve 26 which absorbs the gases which may be produced by a combustion of plastic materials, and finally the layer of metallic oxides 27 in which the carbon monoxide is oxidized and converted to C0 The flow of gas which thus passes out of the first filtration device 20 has been freed from solid particles and also from all toxic compounds which have been retained or converted during the course of its passage through the various layers of filtration, so that this flow of gas is essentially constituted by air charged with CO this CO being formed either during the combustion or by oxidation of carbon monoxide. This mixture of air and CO passes through the suction device 10 from which it proceeds through the interstice between the frusto-conical pressure-reducer l6 and the second nozzle 17. It is then in contact with the alkaline solution which holds back the C0 The purified gaseous fluid thus obtained then passes through the metallic mattress 36 in which it is freed from its moisture, and then returns to the hearth flowing from top to bottom in the conduit 6.

It should be observed that the flow of gas composed of air and CO passes out of the first nozzle 12 at high speed and in laminary flow. It then encounters the second nozzle 17, which, due to its spherical form, converts the laminary flow to a turbulent flow, thus permitting a powerful stirring effect on the gases, which facilitates intimate contact between the CO and the alkaline solution contained in the annular filter 32. This upward turbulent flow of the gaseous mixture in the filtration device 30 has the further advantage of aiding the capillary upward movement of the solution in the filter 32. It should also be noted that the use of a filter impregnated by capillary action of the alkaline solution has the advantage of having practically no loss of pressure.

The purified fluid which is returned to the hearth receives during its passage, by virtue of the orifice 7 provided at the lower part of the conduit 6, a supply of fresh air, adjustable by means of the shutter 7a, which ensures a gaseous mixture suitable for combustion. It will be observed that the re-cycling of the purified flow of gas to the hearth ensures the burning of any carbon monoxide which may subsist, either in the state of traces or in larger proportions, which may accidentally occur in the case where the filter for fixing the carbon monoxide has become saturated. This return to the hearth ensures the complete elimination of the carbon monoxide, and therefore gives complete safety in operation.

There has been shown in FIG. 3 another form of construction of the second filtration device. The filtration device shown, indicated generally by the reference 40, comprises essentially a casing 41 provided internally with a plurality of wicks or thin strips 42 made of a porous material such as blotting paper, these wicks having their lower extremities immersed in an alkaline solution 43 which fills the bottom of the casing 41. The Wicks 42 are thus impregnated by upward capillary action with the alkaline solution. The gaseous mixture consisting of air charged with CO and coming from the sucair then passes through a mattress of metallic fibres in which it is treed by coalescence of the droplets of water which it is conveying. it is then returned to the hearth through the conduit 6.

According to the form or" construction shown i, the second filtration device, indicated gene: y by the reference comprises casing provided at its upper portion with a tank 55a filled v. th an alkaline so lution Flexible capillary strips descend vertically from the bottom v ill of the tank in up to the pro nity of the bottom of the casing The alkaline solution 52 flows down drop by drop by gravity along the strips coming to accumulate at the bottom of the casing The aeous mixture cons! ting of air charged with CO admitted through the pipe 5o nus passes in close contact over the wicics impregnated with alkaline solution, and then passes out of the outlet pi e J I after having been freed from the C0 The supply to the upper tank "la is effected by means of a tube which causes the lower part the casing 5i to communicate with the tank ila, the suction oi the solution being effected by m ans of compressed air supplied for example by the a compressor l and led through pipe opening into the conduit The insoluble carbonates formed by reaction of the (0 with the alkaline solution accumulate at the bottom of the casing 5i, as shown at There has been shown in PEG. 5' another form of construction of the second filtration device oper ing by spraying. The filtration device shown in i1 indicated generally by the reference 66 comprises a casing 6H communicating directly at its upper portion with the first nozzle The casing e1 cont tion 62 which r'ills its lower portion and which is jected directly, by means of a conduit o, i throttle portion .n of the nozrle whi is supplied. as is already known, with cor. pressed air through conduit The ilow oi gas charged with Ct); which passes through the no thus intimately mixed solution thus a-iomi" d in the upper nor the casing The purified air, freed from C out of the casing (ii and underneath the baffle 6 1, using into the chamber as and passing through the metallic mattress do which frees it from its moisture. and then pa s into 6" conduit which leads or to the hearth. The insoluble carbonates are deposited bottom of the casing er, as shown at 6)".

The separation of the CO lay also be bubbling the seous mixture through an lion. t. til

shown in ihe device idicated gene reference 7o. corn a casing '71 proviu with superimposed pla orms '72 containing solution 73 Each platform provided in its cen portion with tubular passage or burst 7 surmounted by a dome Each platform communicates with the platform beneath by an overflow pipe re The .ing flow of gas coming from the nozzle passes throu h the orifices and. due to the presence of the cylinc cal domes compelled to bubble into the all solution of each of the platforms 72. The purified is as b .dv'aiL-ciblG Copy returned to the conduit 6 after having passed through a metallic mattress 77. The precipitate is deposited on the platforms, as shown at Finally, there is shown in MG. '7 another form of construction cf the second filtration device functioning by bub ling into an alkaline solution. The filtration device shown in Fifi. "7., indicated generally by the reference 8 3., comprises essentially a casing 81 which receives from the nozzle 12 the gaseous mixture consisting of air charged with CO inside the casing 81 is placed a receptacle 82 filled with an alkaline solution 83. The receptacle is provided at its lower portion with ball adpermitting the passage of the gasemission valves ous mixture under pressure, consisting of air and CO and discharged from the nozzle 12.

This gaseous mixture passes in the form of bubbles through the alkaline solution in which it becomes freed from its (:0 by the formation of insoluble carbonates. i stir 'ng device or agitator 85, driven in rotation by an electric motor (not shown), causes a turbulent movement oithe solution and in consequence a helicoidal trajectory of the bubbles, which facilitates intimate contact the CO with the said solution. The purified air is sent bacl: through the outlet conduit 86 and the conduit 6- to the hearth 2.

in the form of embodiment shown in FEG. i, the metallic casing 3 plays the part of a heat exchangerv The flow of hot gases coming from the hearth gives up calories to the sheet steel walls which transfer heat in turn to the ambient air. it may however be an advantage, in particular in the of a brick-built fireplace to pro- -ride a heat-exchanger which is arranged directly above the hearth, and through which a fluid to be heated is passed.

Such a fire lace has been shown in FIG. 8, in which the same reference numbers designate the same elements as in PM}. E, the fireplace being provided with suction nd purifying means housed in the masonry conduit Al and provided with a heat-exchanger 91 con sic ing of tubes heated by the combustion gases coming from the hearth before these gases pass into the purifying means. in which tubes the ambient air to be heated is circulated in counterilow.

A depression nozzle 92 connected to the compressor sucks-iii the air from the room through a filter 93 preferably located at the level of the ceiling and delivers it throi. ch a conduit )4- into the exchanger Q i in which it recerves the heat of the combustion gases, and then into the room through a second filter 95 located at the level of the ground. The arrows F indicate the or arse of the There is thus obtained a totalheat replace, the heat of which is entirely recovered and is distributed ii 0 the room, simultaneously by radiation, convection and conduction, whereas in the case of a con ntional fireplace 5 to 20% of the heat is lost.

it is also possible to circulate water in the exchanger so as to supply radiators for heating the premises.

second form of embodiment of a more compact form of the device is shown in PEG. 9.

There can in particular be seen in the first portion of the device a hearth grate 101 on which the combustion is efifected, and under which is provided a drawer 1*? 2 for removing cinders and ash.

The gases generated by the combustion and also the smoke have an upward convection flow and pass through first filter which stops the solid particles.

* iis filter 193 is an element of the first filtration device already referred to. At its outlet into the zone 104, the

flow of gas has a temperature situated in the vicinity of 200C. This flow then passes into the heat-exchanger 105 which is preferably of the type with fins and which occupies the top of the heating device in this form of construction. v

Leaving this exchanger, the flow of gas passes into the second part of the device which is separated from the first by a refractory plate'106. The temperature reached by the flow of gas in the zone 107 is of the order of 30C. There is thus a change from approximately 200C. in the zone 104 to the vicinity of 30C. in the zone 107. Such a cooling action causes a condensation of water vapour and this condensation results in its turn, in this portion of the device, in a depression which accelerates the upward movement of the flow of gas in the first portion of the device.

The flow of gas then passes through the filter 108 which is also an element of the first filtration device and which comprises especially active carbon and various metallic oxides, the function of these latter being to convert the carbon monoxide coming from the combustion to CO carbon dioxide. As shown in FIG. 9, the shape of the filter provides a large surface of contrast between the flow of gases and, in particular the metallic oxides.

The water thus formed is again found in the portion 109, from which a conventional device 1 l enables the water to be extracted when this is considered necessary. In addition, a device 116 known per se makes it possible to prevent the water formed from penetrating into the nozzle 111 and thus compels it to flow directly into the tank 109.

A closed-circuit acceleration nozzle 111 permits the speed of the flow of gas in this portion of the device to be increased by means of the compressor 112, the suction of which is effected above the tank 113. Thus, the flow movement in the entire device is due first of all to convection phenomena and then to a depression, and finally to an acceleration nozzle.

After having been accelerated by the nozzle 111, the flow of gas passes into the second filtration device and bubbles through a solution, for example alkaline, contained in the tank 113. Such a solution may be composed of water, soda and alcohol, but any other solution which can stop the CO is suitable. During the course of this bubbling through an alkaline solution, the CO contained in the flow of gas is precipitated in the form of carbonate.

In order to improve the alkaline solution gas contact, there is arranged a drum 115 constituted by a metal cylinder having its axis of rotation perpendicular to the plane of the drawing. This cylinder is of the wiremesh type permitting effective stirring of the alkaline solution. In addition, this type of drum permits the droplets of water contained in the flow of gas after its passage through the alkaline solution to be stopped.

According to the form of embodiment illustrated in FIG. 9., the gaseous fluid is purified from the CO which it contains by bubbling through an alkaline solution, but this latter may be replaced by any other means permitting contact between the said solution and the carbon dioxide, in particular by the methods illustrated in FIGS. 3 to 7, by the use of a few arrangements so as to permit of their operation.

The purified gas is brought back to the hearth through the conduit 114. However, by reason of the suction necessary for the compressor, there is only very little gas returned to the hearth.

It will of course be understood that numerous alternative forms of the devicesdescribed and shown above may be made, without thereby departing from the scope of the invention.

What I claim is:

1. A gas circulating and purifying device in combination with a fireplace having a hearth open to the atmosphere and on which combustion is effected, said device comprisirig:

means defining a path for gases extending from an inlet in the upper part of said fireplace to an outlet in its lower part leading to said hearth,

suction means in said path for creating a flow of the gaseous mixture formed by said combustion from said inlet toward said outlet, said suction means comprising a static nozzle in said path and means for directing a flow of fluid under pressure through said nozzle to create a depression upstream of said nozzle, and

purifying means in said path for separating entrained particles from said gaseous mixture and for absorbing noxious gases from said mixture.

2. A device as claimed in claim 1, in which said purifying means comprise a first and a second filtration devices disposed respectively upstream and downstream of said nozzle.

3. A device as claimed in claim 2, in which said first filtration device comprises successively, in the direction of flow of said gaseous mixture, means for retaining said solid particles, gas-absorption means for noxious gases means for removing water vapour, porous means forming a molecular sieve for the retention of gaseous molecules of pre-determined size, and catalytic means for the conversion of carbon monoxide to carbon dioxide.

4. A device as claimed in claim 3, in which said particle-retention means are constituted by a mattress of steel wires.

5. A device as claimed in claim 3, in which said partiole-retention means are constituted by a mattress of material chosen from the group consisting of silica fibres and alumina fibres.

6. A device as claimed in claim 3, in which said absorption means are constituted by active carbon.

7. A device as claimed in claim 3, in which said means for removing water vapour remaining in the gases are dehydrated substances with a micro-porous structure.

8. A device as claimed in claim 3, in which said catalytic means are constituted by a plurality of metallic oxides selected from the group consisting of manganese dioxide, copper oxide, cobalt oxide and silver oxide.

9. A device as claimed in claim 2, in which said second filtration device comprises means for retaining CO 10. A device as claimed in claim 9, in which said CO retaining means especially comprise an alkaline solution.

11. A device as claimed in claim 10, in which said CO retaining means also comprise an element with a capillary structure in contact with said alkaline solution, said element located in said path.

12. A device as claimed in claim 11, in which said element is constituted by a herringbone filter, the base of which is immersed in said alkaline solution.

13. A device as claimed in claim 11, in which said element is constituted by a plurality of wicks, the base of which is immersed in said alkaline solution.

14. A device as claimed in claim 1 l, in which said element is constituted by a plurality of strips, the upper portions of which are immersed in a receptacle containing said alkaline solution. i

15. A device as claimed in claim 10, in which said CO retaining means are constituted by a receptacle containing the alkaline solution and connected by a conduit to the first nozzle, the CO being eliminated by atomization of said solution in the gaseous mixture passing through said nozzle.

16. A device as claimed in claim 10, in which said CO retaining means comprises an assembly of superimposed tanks containing an alkaline solution through which the gaseous mixture is successively bubbled.

17. A device as claimed in claim 10, in which said CO retaining means are constituted by a receptacle containing said alkaline solution, through which the gaseous mixture is bubbled.

18. A device as claimed in claim 17, further comprising a rotating agitator mounted inside said receptacle and adapted to stir said solution.

19. A device as claimed in claim 18, in which said agitator is a wire-mesh drum having a horizontal axis of rotation.

20. A device as claimed in claim 9, comprising a mattress of steel wires adapted to cause the condensation of droplets of solution carried away by the flow of gas.

21. A device as claimed in claim 1, said device further comprising heat-exchanger means.

22. A device as claimed in claim 16, in which said heat-exchanger means comprises fins.

23. A device as claimed in claim 1, in which said suction means comprise a second static nozzle downstream of said first-mentioned nozzle and consisting of a part-spherical member coaxial with said firstmentioned nozzle and having a convex side facing said first-mentioned nozzle to form a deflecting surface for the gaseous mixture arriving from said first-mentioned noule, and cause a turbulent flow of said gaseous mixture at the outlet of said second nozzle. 

1. A gas circulating and purifying device in combination with a fireplace having a hearth open to the atmosphere and on which combustion is effected, said device comprising: means defining a path for gases extending from an inlet in the upper part of said fireplace to an outlet in its lower part leading to said hearth, suction means in said path for creating a flow of the gaseous mixture formed by said combustion from said inlet toward said outlet, said suction means comprising a static nozzle in said path and means for directing a flow of fluid under pressure through said nozzle to create a depression upstream of said nozzle, and purifying means in said path for separating entrained particles from said gaseous mixture and for absorbing noxious gases from said mixture.
 2. A device as claimed in claim 1, in which said purifying means comprise a first and a second filtration devices disposed respectively upstream and downstream of said nozzle.
 3. A device as claimed in claim 2, in which said first filtration device comprises successively, in the direction of flow of said gaseous mixture, means for retaining said solid particles, gas-absorption means for noxious gases means for removing water vapour, porous means forming a molecular sieve for the retention of gaseous molecules of pre-determined size, and catalytic means for the conversion of carbon monoxide to carbon dioxide.
 4. A device as claimed in claim 3, in which said particle-retention means are constituted by a mattress of steel wires.
 5. A device as claimed in claim 3, in which said particle-retention means are constituted by a mattress of material chosen from the group consisting of silica fibres and alumina fibres.
 6. A device as claimed in claim 3, in which said absorption means are constituted by active carbon.
 7. A device as claimed in claim 3, in which said means for removing water vapour remaining in the gases are dehydrated substances with a micro-porous structure.
 8. A device as claimed in claim 3, in which said catalytic means are constituted by a plurality of metallic oxides selected from the group consisting of manganese dioxide, copper oxide, cobalt oxide and silver oxide.
 9. A device as claimed in claim 2, in which said second filtration device comprises means for retaining CO2.
 10. A device as claimed in claim 9, in which said CO2 retaining means especially comprise an alkaline solution.
 11. A device as claimed in claim 10, in which said CO2 retaining means also comprise an element with a capillary structure in contact with said alkaline solution, said element located in said path.
 12. A device as claimed in claim 11, in which said element is constituted by a herringbone filter, the base of which is immersed in said alKaline solution.
 13. A device as claimed in claim 11, in which said element is constituted by a plurality of wicks, the base of which is immersed in said alkaline solution.
 14. A device as claimed in claim 11, in which said element is constituted by a plurality of strips, the upper portions of which are immersed in a receptacle containing said alkaline solution.
 15. A device as claimed in claim 10, in which said CO2 retaining means are constituted by a receptacle containing the alkaline solution and connected by a conduit to the first nozzle, the CO2 being eliminated by atomization of said solution in the gaseous mixture passing through said nozzle.
 16. A device as claimed in claim 10, in which said CO2 retaining means comprises an assembly of superimposed tanks containing an alkaline solution through which the gaseous mixture is successively bubbled.
 17. A device as claimed in claim 10, in which said CO2 retaining means are constituted by a receptacle containing said alkaline solution, through which the gaseous mixture is bubbled.
 18. A device as claimed in claim 17, further comprising a rotating agitator mounted inside said receptacle and adapted to stir said solution.
 19. A device as claimed in claim 18, in which said agitator is a wire-mesh drum having a horizontal axis of rotation.
 20. A device as claimed in claim 9, comprising a mattress of steel wires adapted to cause the condensation of droplets of solution carried away by the flow of gas.
 21. A device as claimed in claim 1, said device further comprising heat-exchanger means.
 22. A device as claimed in claim 16, in which said heat-exchanger means comprises fins.
 23. A device as claimed in claim 1, in which said suction means comprise a second static nozzle downstream of said first-mentioned nozzle and consisting of a part-spherical member coaxial with said first-mentioned nozzle and having a convex side facing said first-mentioned nozzle to form a deflecting surface for the gaseous mixture arriving from said first-mentioned nozzle, and cause a turbulent flow of said gaseous mixture at the outlet of said second nozzle. 